(M1230-03-15) Coamorphous Nanoparticles Produced by Co-precipitation of Two Drugs Based on Liquid-Liquid Phase Separation: Improved Solubility and Membrane Permeability

Purpose: The coamorphous is an amorphous state in stoichiometric binary systems of two compatible compounds between drug and coformer¹⁾. The formation of coamorphous contributes to enhancing the solubility and oral absorption of the target drugs. Dry milling and spray-drying methods are normally used to prepare coamorphous particles. The particle sizes prepared by those methods are often limited in the order of micrometers. It is reported that nanoparticles can penetrate deeply into the intestinal membrane and enhance the drug permeability²⁾. In this study, the coamorphous nanoparticles were investigated by co-precipitation of two drugs based on liquid-liquid phase separation (LLPS). The effect of coamorphous nanoparticles formation on solubility and membrane permeability was investigated.

Methods: Atorvastatin calcium hydrate (ACT) and nifedipine (NDP) were used as model drugs. Their combination is used as combination therapy for lifestyle disease treatment. ACT and NDP were dissolved in methanol as a molar ratio of 2:1, 1:1 and 1:2. The methanolic drugs solution (50 mg/mL as ACT content) was added into 0.1% PVA aqueous solution using peristaltic pump at a flow rate of 10 ml/min. Then, the formed dispersion was immediately centrifuged for 10 min at 4◦C and 50,000 rpm using a high speed refrigerated centrifuge. The obtained residue was redispersed in distilled water with sonication. The final dispersion was subjected to freeze drying for 24 h. The crystallinity of freeze-dried powder was evaluated by powder X-ray diffraction measurement. The particle size of the freeze-dried samples was determined after dispersion in distilled water by dynamic light scattering method with Litesizer 500. Phase behavior of supersaturated solutions of drugs were evaluated using μDISS system. The solubility and permeability of drugs was evaluated by μFlux system. Test concentration of μFlux system was set to 50 μg/mL as NDP concentration.

Results: When the methanolic solution of ATC alone or NDP alone was added into aqueous solution, their particle sizes were in the micrometer range (Table 1). The mixture of ATC and NDP resulted in a particle size reduction of both drugs to nano-range. Especially, the NDF:ATC (1:2) maintained the nanoparticles without aggregation after freeze drying. The all freeze-dried powders (FDPs) of NDP:ATC and ATC alone showed the amorphous state. In the FDPs of NDP alone, the crystal peaks originating from NDP was observed. To elucidate the phase behavior of supersaturated solutions, UV measurement was performed in 0.1% PVA solution using μDISS system (Figure 1). The LLPS concentration of NDP from NDP alone and NDP:ATC mixture were ca. 130 μg/mL and 260 μg/mL, respectively. In the case of ATC, the LLPS concentration from ATC alone and NDP:ATC mixture were ca. 730 μg/mL and 810 μg/mL, respectively. These results indicated that the coexistence of both drugs stabilizes the supersaturation of both drugs. Supersaturated state may be stabilized by the penetration of the opposite drug into the drug-rich phase. The dissolution and permeability of both drugs were evaluated by the μFlux system (Figure 2). The untreated NDP powder showed a low dissolution rate and NDP concentration in the donor chamber, followed by a low permeated amount of NDP in the acceptor chamber. FDPs of NDP:ATC (1:2) maintained the NDP concentration after supersaturation in the donor chamber. The permeated amount of NDP from FDPs of NDP:ATC (1:2) was 4-times higher than that of untreated NDP powder. On the other hand, ATC concentration in the donor chamber and permeation amount of ATC was little changed between untreated ATC powder and FDPs of NDP:ATC (1:2). This result was estimated by the high solubility of ATC compared to NDP.

Conclusion: The coexistence of NDP and ATC allowed the preparation of amorphous nanoparticles. These prepared amorphous nanoparticles enhanced solubility and permeability of NDP.

References: 1) Nascimento, A.L.C.S., Martins, I.C.B., Spósito, L., Morais-Silva, G., Duarte, J.L., Rades, T., Chorilli, M., 2024. Indomethacin-omeprazole as therapeutic hybrids? Salt and co-amorphous systems enhancing physicochemical and pharmacological properties. International Journal of Pharmaceutics 653, 123857.
2) Imono, M., Uchiyama, H., Yoshida, S., Miyazaki, S., Tamura, N., Tsutsumimoto, H., Kadota, K., Tozuka, Y., 2020. The elucidation of key factors for oral absorption enhancement of nanocrystal formulations: In vitro–in vivo correlation of nanocrystals. European Journal of Pharmaceutics and Biopharmaceutics 146, 84–92.

Acknowledgements: The authors thank Anton Paar (Austria) for lending Litesizer 500. There are no fundings and conflict of interest.


Figure 1 Simultaneous determination of LLPS concentration of ritonavir in water at 37 ℃ using a μDISS system.


Figure 2 Schematic presentation of one donor-acceptor pair of the µFluxTM apparatus separated by a membrane with UV-vis probes and dissolution and permeation profile of NDC.


Table 1 Particle size of NDP and ATC before and after freeze drying.